|
Decay progresses in wood at about the same rate as growth, going chiefly in and down instead of out and up. When its invasion at a stub lesion has gone past the sap-wood into heartwood, you will not only have to gouge out the decay's top and back limits but also follow its inroads downward to their bottom, which may be surprisingly deep. That is where little stub lesions deceive us. In trying to heal shut at their original openings, they conceal their true depth and thus escape or postpone attention. To find out how deep the decay has gone, enlarge the original opening enough to let you probe downward with your knife or chisel. If you still can't find hard bottom, take test borings from the outside with a quarter-inch auger, slanting the bit upward so that the hole will drain when you do get a bottom one. What you do next will depend on several things, but your main objects will stay the same: to clean out all the punky wood possible, paint all the exposed good wood that you can reach, and establish free drainage of the cavity. If the decay goes back into heartwood only a short distance and downward no farther than your chisel can reach, you may elect simply to cut open an exterior V channel through which you can be sure of excavating and painting
thoroughly. (See Fig. 9.) If the cavity's vertical depth is great, you may decide to establish drainage by enlarging your test hole and inserting a tube (copper or galvanized), meantime carving back the cavity's upper wall surfaces as best you can. (See Fig. 10.) Often this compromise is best, to avoid an ugly gape in the tree and conserve the sapwood shell. The decay remaining within can be slowed by flushing out the cavity with disinfectant (copper sulphate or mercury bichloride solution), and this process will give you a check on your drainage, through the tube. A dry hole rots much more slowly than a damp one. |
|||
|
